ENV 101 Ch03 lecture ppt_a

3-1
Environmental
Geology
James Reichard
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

3-2
Chapter 3
Earth Materials
© Image Ideas/PictureQuest

3-3
Basic Building Blocks (1)
Atoms
• Nucleus contains protons and neutrons
• Electrons orbit the nucleus
Elements
• Atoms with the same number of protons
• Hydrogen has one proton, Helium has two

3-4
Jump to long description

3-5

3-6

3-7
Minerals (1)
• Naturally occurring
• Inorganic
• 1 or more element
• Solid, crystalline structure

3-8
Minerals (2)
• 4,000+ minerals
• Each has unique chemical
and physical properties
• Building blocks of rocks
© Doug Sherman/Geofile

3-9
Same composition different structure

3-10
Silicates

3-11
Rock Forming Minerals
• Approximately 12 common minerals make
up crust
• Pyroxene and Amphibole are
ferromagnesian silicates
• Feldspars
• Clay minerals
• Quartz
• Calcite
(a–d): © J. Geisler

3-12
Rocks
Aggregate or assemblage of one or more
mineral
Three types
• Igneous
• Sedimentary
• Metamorphic
(a–b): © J. Geisler

3-13
Igneous Rocks (1)
Form via cooling magma/lava
Extrusive cooled
• Fine grained
Intrusive cooled
• Coarse grained
(a-c): © Jim Reichard

3-14
Igneous Rocks (2)
Once magma reaches the surface it is
called lava.
R.L. Christiansen/USGS
Jump to long
description

3-15
Igneous Rocks (3)
Jump to long
description

3-16
Weathering (1)
Breaking down of rocks
• Physical weathering
• Frost wedging
• Plant roots
• Crystal growth
• Heat
b: Marten Geertsema, Geologic Survey of Canada

3-17
Weathering (2)
Breaking down of rocks
• Chemical
• Dissolution
• Hydrolysis
• Oxidation / reduction
a: © The McGraw-Hill Companies, Inc./Louis Rosenstock, photographer; b: ©
Royalty Free/Corbis
Jump to long
description

3-18
Weathering (3)
Dissolution: A process in which minerals dissolve in water. Water itself is not broken down and there is no remaining solid, only
dissolved ions—water is included in the reactions below simply to show it is present. Increased acidity (H+
ions) is
required for some minerals such as calcite to dissolve.
NaCl
(halite)
+ H2O →
Na+
(sodium ions)
+
Cl−
(chlorine ions)
+ H2O
CaCO3
(calcite)
+
H2CO3
(carbonic acid)
+ H2O →
Ca2+
(calcium ions)
+
2HCO3
−
(bicarbonate ions)
+ H2O
Hydrolysis: A reaction between water and a mineral in which water itself is broken down into hydrogen and oxygen. Here a
completely new mineral is formed as ions are released into solution. Note that hydrolysis reactions require an
acidic solution such as natural rainwater.
4KAlSi3O8
(orthoclase feldspar)
+
4H2CO3
(carbonic acid)
+ 18H2O →
4K+
(potassium ions)
+
4HCO3
−
(bicarbonate ions)
+
Al2Si4O10(OH)8
(kaolinite)
+
8H4SiO4
(silicic acid)
Oxidation/Reduction: A reaction in which electrons are transferred between compounds—commonly involves free oxygen O2 .
Note that one compound gains electrons and the other loses electrons.
3FeS2
(pyrite)
+
11O2
(free oxygen)
+ 6H2O →
Fe2O3
(hematite)
+
6H2SO4
(sulfuric acid)
Jump to long
description

3-19
Sedimentary Rocks (1)
Made of sediment, compacted and
cemented
• Detrital
• Shale, sandstone
• Chemical
• Limestone, rock salt
A. Coconino sandstone, Grand Canyon
B. Sandstorm approaching a town in Africa C. Death Valley, California
a: © Jim Reichard; b: © MarketPlace/Media Bakery; c: © Royalty Free/Corbis

3-20

3-21
a: © Norris Jones; b: © Charlie Jones; (inset): Courtesy of Stan Celestian
© Charlie Jones

3-22
Fossiliferous limestone
formation
a: © Cavan Images/Getty Images

3-23
© John Karpovich/University of Virginia
© William Perry/age fotostock; (inset) © Doug Sherman/Geofile

3-24
Metamorphic Rocks
Changes through heat and
pressure, not enough to melt
rock
• Contact metamorphism
• Heat, low pressure
• Nonfoliated texture, marble and
quartzite
• Regional metamorphism
• Heat, high pressure
• Foliated texture, slate and gneiss

3-25
Regional Metamorphism
(inset): © Siim Sepp/Alamy

3-26
Foliation
(a-c): © J. Geisler

3-27
Rock Cycle

3-28
Rocks as Indicators of the Past
A. Zion National Park, Utah
B. Glacier National Park, Montana
(a-b): © Jim Reichard
© Jim Reichard

3-29
Rocks (and Minerals) as
Indicators of the Past
JW Valley - Univ. Wisconsin - Madison

3-30
Sedimentary Features on Mars
NASA/JPL/Malin Space Science Systems Jump to long description

Appendix of Image Long
Descriptions

Basic Building Blocks (2) Long Description
In a simplified view of atoms, negatively charged electrons orbit a nucleus composed of much larger protons
(positive charge) and neutrons (neutral). The simplest types of atoms are of the element hydrogen (A), with a
single electron orbiting a proton. Each succeeding element in the periodic table contains an additional proton and
varying numbers of neutrons, thereby making those elements heavier. A carbon atom (B) contains roughly the
same numbers of neutrons and electrons as it does protons.
Jump back to slide containing original image

Illustration showing the three isotopes of the element hydrogen. The lightest isotope, common hydrogen,
contains only a single proton in the nucleus. Deuterium and tritium are progressively heavier isotopes that have
one and two neutrons, respectively, along with a single proton. A superscript next to the chemical symbol (i.e.,
1H, 2H, 3H) represents the number of protons and neutrons in the nucleus, which indicates the mass
of the atom.

Earth has a layered structure (A) consisting of the core, mantle, and crust. Geologic processes have caused the
heaviest elements to become concentrated in the core over time, whereas the lighter elements have tended to
accumulate in the crust. Pie diagrams (B) show that the crust is largely composed of oxygen and silicon atoms,
but in the planet as a whole, iron atoms are the most abundant.

Minerals (1) Long Description
All minerals have an internal structure and a definite chemical composition where the atoms are arranged in a set
pattern that repeats itself in a three-dimensional manner. In view (A) the distance between atoms has been
exaggerated to illustrate the fact that the angles and distances within the crystal structure are fixed. Also note
that the surface of each atom represents the outermost shell or cloud of the atom’s electrons.

Minerals (2) Long Description
Minerals can grow crystal faces, as in these quartz crystals, provided there is sufficient space for he faces to
develop.

Same composition different
structure Long Description
Although both diamond and graphite are composed entirely of carbon atoms, they have different crystalline
structures. Diamond’s structure helps make it the hardest known substance, whereas the weak bonds between
the sheets of carbon atoms in graphite make it one of the softest minerals.

SilicatesLong Description
Minerals in the silicate class all have the silicon-oxygen tetrahedron as their basic building block, which can be
linked together in the various ways shown here.

Rock Forming Minerals Long Description
Some of the more important rock-forming minerals: (A) olivine, an iron and magnesium-rich silicate believed to
be compositionally similar to the minerals making up the mantle; (B) feldspars, a mineral group that makes up
the largest percentage of crustal rocks; (C) quartz, a very abundant mineral in continental rocks and sediment;
and (D) micas, a group of common platy minerals.

Rocks Long Description
Rocks are commonly composed of multiple types of mineral grains like the granite in (A), but some contain only
a single type of mineral grain, as in the quartzite shown in (B).

Igneous Rocks (1) Long Description
Volcanic glass (A) is an extrusive rock that cooled from magma so fast that the atoms were not able to establish
a crystalline structure and form minerals. Other extrusive rocks such as basalt (B) cool slowly enough that small
mineral crystals are able to develop, but are too small to be visible with the naked eye. Intrusive rocks like
granite (C) cool much more slowly, allowing mineral grains to grow to the point that they are clearly visible.

A lava lake developed inside the crater of Hawaii’s Kilauea volcano. When lava is exposed to the surface
environment, it cools quickly, resulting in fine-grained igneous rocks.

The classification of igneous rocks is based on texture and mineral composition. Of the various rock types,
granites and basalts are the most common igneous rocks in Earth’s crust.

Weathering (1) Long Description
One of the ways physical weathering occurs is when water repeatedly freezes and expands within a fracture (A),
slowly wedging the rock into smaller pieces. This breakage causes the surface area of the rock body to increase
dramatically, thereby increasing the area where chemical weat+E15hering can take place. Photo (B) shows a
large slab of rock slowly being wedged away from a rock body in British Columbia, Canada.

Materials made of the mineral calcite, such as this tombstone (A), readily break down by dissolution reactions
with acidic rainwater. The iron found in automobiles (B) undergoes oxidation/reduction reactions and forms a
variety of secondary minerals collectively known as iron oxides.

Important types of chemical reactions involved in the chemical weathering of minerals. Example reactions are
shown for a few of the more common minerals that undergo chemical decomposition.

Sedimentary Rocks (1) Long Description
Sediment that forms by the weathering of rocks is normally transported to some other site where it is deposited.
Given the right conditions, the deposit may turn into sedimentary rocks. Example photos show massive
sandstone rock (A) that represents ancient sand dune deposits, active wind transport of sediment (B), and a
windblown sand deposit (C).

Weathering and erosion generate sediment that is ultimately transported to a depositional site where it settles
out of the water column and accumulates. Here the sediment is sorted by grain size, becomes buried, and
undergoes compaction. Layers of solid rock form when mineral precipitation cements the grains together. Note
how the layers do not grow laterally after a certain point, but slowly change into other rock types as grain size
changes.

A. Detrital sedimentary rock called conglomerate (A) consists of coarse rock and mineral fragments, which
represent sediment that is young and has not traveled far. As the transport distance increases, feldspar and
ferromagnesian minerals in the fragments break down into clay particles, whereas quartz remains unaltered
and tends to dominate the grain size called sand. Photo (B) shows a sandstone rock composed almost
entirely of quartz grains.
B. Many marine organisms create body parts made of calcite by extracting dissolved ions from seawater. Their
skeletal remains can accumulate on the seafloor over time to form fossiliferous limestone, like the rock
shown here.

Fossiliferous limestone
formation Long Description
Fossiliferous limestone typically forms where the water column is free of suspended sediment (A), allowing
calcite-producing marine organisms to thrive. Limestone forms in shallow seas beyond the point where sediment
settles out to form detrital rocks (B) or in nearshore areas where there is minimal sediment influx (C).

a) The exposed limestone rocks of the Guadalupe Mountains in Texas are approximately 250 million years old
and were once part of an extensive marine reef system.
b) Death Valley in California once held a freshwater lake that eventually evaporated, causing the concentration
of dissolved ions to become so great that minerals began to precipitate. Shown here is an evaporite deposit
of mostly rock salt (halite) covering the valley floor.

Metamorphic Rocks Long Description
When magma comes into contact with rocks, the increased heat can cause minerals to recrystallize into larger
grains and/or be transformed into more stable minerals. The width of the metamorphic alteration zone
depends on how susceptible the original minerals are to higher levels of heat.

Regional Metamorphism Long Description
Regional metamorphism commonly occurs when deeply buried rocks are subjected to compressive forces.
Elevated levels of both heat and pressure cause minerals within the rocks to recrystallize or be transformed into
more stable minerals. The directed pressure forces elongated and platy minerals to become aligned, giving the
rock a foliated (layered) texture. At higher levels of heat and pressure, rocks may begin to deform by flowing in
the solid state (plastic flow) as opposed to fracturing in a brittle manner. At high enough temperatures the rocks
can begin to melt and form magma.

Foliation Long Description
The increased pressure associated with regional metamorphism gives rocks a foliated texture where platy and
elongated minerals are aligned in a parallel manner. Photos showing examples of some of the more common
types of foliated metamorphic rocks.

Rock Cycle Long Description
The rock cycle explains how various geologic processes can cause rocks to be transformed into different types of
rocks. The geologic processes that operate within the rock cycle ultimately cause the rocks within Earth’s crust to
be recycled over time.

Rocks as Indicators of the Past Long Description
a) Features preserved in sedimentary rocks hold important clues as to the environment where the original
sediment was deposited. The cross-bedding of layers in (A) is the result of windblown sand being deposited
in shifting sand dunes. The ancient mudcracks in (B) developed in clay-rich sediment deposited in a shallow
lake that periodically dried up.
b) A 400-million-year-old fossiliferous limestone from the Great Lakes region in North America proves that life
flourished in the marine environment that once existed in the area.

Rocks (and Minerals) as
Indicators of the Past Long Description
a) Radiometric dating of this zircon crystal, from Australia’s Jack Hills region, indicates that it crystallized from
cooling magma 4.4 billion years ago and was once part of Earth’s original crust. The crystal, only 0.4 mm in
length, was liberated from the crust by weathering and erosion and incorporated into sediment, which was
then transformed into sedimentary rock before undergoing regional metamorphism. This crystal tells us that
the hydrologic and rock cycles must have been active early in Earth’s history.
b) Illustration showing where the Jack Hills zircon crystal falls along Earth’s 4.6-billion-year timeline. Other
major events shown here are based on evidence contained in Earth’s rock record along with rocks from the
Moon and Mars. Note that the majority of the fossil record lies within the most recent 500 million years of
the Phanerozoic Eon.

Sedimentary Features on Mars Long Description
Image of Mars taken from an orbiting spacecraft, showing what appear to be sedimentary rocks and an ancient
shoreline.

ENV 101 Ch03 lecture ppt_a

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to ENV 101 Ch03 lecture ppt_a

Similar to ENV 101 Ch03 lecture ppt_a (20)

More from BHUOnlineDepartment

More from BHUOnlineDepartment (20)

Recently uploaded

Recently uploaded (20)

ENV 101 Ch03 lecture ppt_a